In a unit being an optical system base unit for a concentrator photovoltaic, a concentrating portion composed of a Fresnel lens forms a light spot by converging sunlight to be guided to a small cell, whereby power is generated. For such a cell, a solar cell having a high power generating efficiency and heat resisting property is used. Such a configuration allows much light energy to be concentrated onto a small cell, whereby power can be generated with high efficiency. A large number of such concentrator photovoltaic units are arranged in a matrix shape to form a concentrator photovoltaic module, and then, a large number of the modules are arranged in a matrix shape to form a concentrator photovoltaic panel. The concentrator photovoltaic panel forms a concentrator photovoltaic apparatus, together with a driving device for causing the panel to perform tracking operation while facing the sun.
In order to accurately direct the light spot onto the small cell, it is necessary to cause the concentrating portion to always and accurately face the sun, to allow sunlight to be incident on the concentrating portion in parallel to the optical axis of the concentrating portion, at an incidence angle of 0 degrees. However, actually, due to deviation in tracking operation and variation in accuracy of parts, there are cases that the incidence angle is not 0 degrees. Since the concentrator photovoltaic panel does not track the sun during night time, there are cases where, at first in the morning, tracking operation is delayed for the power generation and the incidence angle is not 0 degrees.
When such an incidence deviation angle occurs, power generating efficiency is reduced, and strong light strikes the vicinity of the cell, thereby causing early degradation of the material of that portion.
Thus, it has been proposed to provide a homogenizer (pillar-shaped optical member) for guiding light to the cell even with the presence of a slight deviation angle (for example, see PATENT LITERATURE 1 (FIG. 4)). It has also been proposed to provide a shield plate between the concentrating portion and the cell in addition to the homogenizer, to suppress strong light from striking the vicinity of the cell.